Contact probe

ABSTRACT

A contact probe comprises a tip portion for making contact with a subject surface, a supporting portion, and a spring portion for connecting the other two members. The tip portion has a corner portion whose radius of curvature is larger than that of the opposite corner portion that moves in the lead during the scrubbing by the pressing force. The insulating layer on the subject surface is sufficiently removed by the scrubbing to secure the electrical contact, and the amount of shavings is minimized during the dissociation of the contact probe. Formation of scratches on the subject surface is reduced. Another contact probe for a ball-shaped electrode has a tip portion with a recess, which has a protrusion and bottom. The protrusion breaks the insulating layer on the electrode to secure the electrical contact. The bottom makes contact with the electrode to prevent the protrusion from excessively biting the electrode.

RELATED APPLICATION

This application is a 371 of PCT/JP 02/10563 filed on Oct. 10, 2002under No. PCT/JP02/10563.

TECHNICAL FIELD

The present invention relates to a contact probe for electricallyinspecting semiconductor substrates, liquid-crystal displaying devices,and other devices.

BACKGROUND ART

Inspection of the electric circuits formed for semiconductor substrates,liquid-crystal displaying devices, and other devices is usuallyconducted by using an inspecting apparatus provided with a multitude ofcontact probes. The surface of a circuit to be measured (hereinafterreferred to as a subject surface) is usually covered by an insulatinglayer, such as a naturally formed oxide layer or resist residues. Tocarry out the inspection, it is necessary to break the insulating layerto secure reliable electrical contact with the electrode of the circuitunderneath the insulating layer. Two methods have been employed to breakthe insulating layer. One is to scrub along the subject surface toremove the insulating layer so that the electrical contact with theelectrode underneath can be secured. The other is to press a sharp edgeagainst the insulating layer to penetrate through it.

In this specification, the term “scrub” is used to mean to scrub asubject surface by using a sharp edge. Researchers and engineers haveproposed a process known as the lithographie galvanoformung abformung(LIGA) process for forming a contact probe that performs the foregoing“scrubbing.” According to this process, a contact probe is formed bylithography and plating using a mask having a specified pattern asexplained in the published Japanese patent application Tokukai2001-343397, for example.

Examples of the conventional shape of contact probes formed by the LIGAprocess are shown in FIGS. 12 and 13. These contact probes comprise atip portion 1 for making contact with a subject surface 20, a springportion 2 having a bent portion, and a supporting portion 3 forsupporting the contact probe attached to an inspecting apparatus. Theshape of the spring portion 2 is not limited to the unidirectionallybending shape as shown in FIGS. 12 and 13; an S shape or a waving shapealso can be used. As shown in FIG. 14, a contacting flat face 10 isprovided at the lowermost part of the tip portion 1. An oblique face 15is provided at each side of the contacting flat face 10. When thesupporting portion 3 of the contact probe shown in FIG. 12 is fixed toan inspecting apparatus and when the contact probe is pressedperpendicularly against the subject surface 20, the contacting flat face10 of the tip portion 1 makes area contact with the subject surface 20,and the spring portion 2 deforms elastically in a direction shown by anarrow 31. During this elastic deformation, the posture of the tipportion 1 is constrained by the force that presses it against thesubject surface 20. Consequently, the tip portion 1 moves in a directionshown by an arrow 32 nearly maintaining the posture of the area contactwith the subject surface 20. Thus, the “scrubbing” is performed.

The performance of the contact probe shown in FIG. 13 is similarlyexplained below. When the supporting portion 3 of the contact probe isfixed to an inspecting apparatus and when the contact probe is pressedperpendicularly against the subject surface 20, the contacting flat face10 of the tip portion 1 makes area contact with the subject surface 20,and the spring portion 2 deforms elastically in a direction shown by anarrow 33. During this elastic deformation, the posture of the tipportion 1 is constrained by the force that presses it against thesubject surface 20. Consequently, the tip portion 1 moves in a directionshown by an arrow 34 nearly maintaining the posture of the area contactwith the subject surface 20. Thus, the “scrubbing” is performed.

The moving direction of the tip portion 1 pressed against the subjectsurface 20 is determined by the shape and the relative position of thetip portion 1, the spring portion 2, and supporting portion 3 when thecontact probe is formed as a unitary structure with the same material.When different materials are used for individual portions, the types ofthe materials are also a factor to determine the direction.

A series of the operation from the start of the contact of the tipportion 1 with the subject surface 20 to the end of the contact isexplained in detail below by referring to FIGS. 15 to 17. In the case ofthe example shown in FIG. 15, the subject to be measured is a substrate21 provided with an aluminum electrode 22 on the surface. The surface ofthe aluminum electrode 22 is the subject surface 20. The surface of thealuminum electrode 22 is covered with a naturally formed oxide layer 25.As shown in FIG. 15, the tip portion 1 of the contact probe descendsfrom immediately above in order for the contacting flat face 10 to makecontact with the subject surface 20. As shown in FIG. 16, the elasticdeformation of the spring portion 2 (not shown in FIG. 16) moves the tipportion 1. In the case of the example shown in FIG. 16, the tip portion1 is assumed to move to the right. In this case, because the tip portion1 is pressed against the subject surface 20, it moves to the rightmaintaining the posture of the contact between the contacting flat face10 and the subject surface 20. Thus, the “scrubbing” is performed.During this operation, the tip portion 1 scrubs away the oxide layer 25,forming scratches 24. Under this condition, the tip portion 1 can securethe electrical contact with the aluminum electrode 22 previously coveredby the oxide layer 25, enabling the measurement through the contactprobe.

After the measurement, the contact probe ascends. However, the tipportion 1 does not ascend directly from the position shown in FIG. 16.As shown in FIG. 17, as the spring portion 2 decreases its elasticdeformation, the tip portion 1 moves to the left while continuing toscrub the surface and then moves upward.

As shown in FIGS. 16 and 17, the scrubbing allows shavings 23 of thealuminum electrode 22 and the oxide layer 25 to adhere to the tipportion 1. Every measurement with the contact probe requires theoperations shown in FIGS. 15 to 17. The shavings 23 adhere to the tipportion 1 not only when the scrubbing is performed by pressing thecontact probe to the subject surface 20 as shown in FIG. 16 but alsowhen the scrubbing is performed during the dissociation of the contactprobe from the subject surface 20 as shown in FIG. 17. The latterscrubbing does not contribute to the measurement, although it isinevitable. The adhering shavings 23 decrease the quality of theelectrical contact of the contact probe in the next measurement.Consequently, to maintain good electrical contact to a certain extent,it is necessary to clean the tip portion 1 after a certain number ofmeasurements are carried out, for example, 1,000 times. The cleaningrequires discontinuation of the measurement, thereby decreasing theproductivity.

Excessive adherence of the shavings 23 diminishes the measurementaccuracy, and a good product may be judged as unsatisfactory. Thismisjudgment causes an otherwise unnecessary reduction of yield.

Furthermore, as described above, the tip portion 1 produces thescratches 24 on the subject surface 20 not only when the scrubbing isperformed by pressing the contact probe against the subject surface 20for securing the electrical contact as shown in FIG. 16 but also whenthe scrubbing is performed during the dissociation of the contact probefrom the subject surface 20 after the measurement as shown in FIG. 17.Consequently, the scratches 24 on the surface of the aluminum electrode22 grow in excess of the extent necessary to break the insulating layer.The excessive scratches may cause unsatisfactory bonding between thealuminum electrode 22 and a gold wire in the subsequent ultra-sonicbonding process, because the alloying process between the aluminumelectrode 22 and the gold wire does not proceed properly.

In addition, the subject surface is not necessarily a flat surface. Itmay be a curved surface, such as the surface of a ball. For example, aball grid array (BGA) package 70 shown in FIG. 28 requires measurementby making contact with solder balls 72 arranged on the undersurface of aBGA substrate 71. Several contact probes have been proposed for theinspection through the foregoing solder balls 72. These contact probesand problems caused by them are explained below.

A first prior art for a ball-shaped subject surface uses a contact probe100 shown in FIG. 29, which is one of the POGO® pin types. The contactprobe 100 comprises a tip portion 121 for making contact with a subjectsurface and a spring portion 122 for connecting the tip portion 121 to acylindrical supporting portion 123. The contact probe 100 is produced bymachining. The tip portion 121 and the supporting portion 123 basicallyhave a cylindrical shape, and the upper end of the tip portion 121 has aconical shape. The spring portion 122 is made of a coil spring. As shownby an arrow in FIG. 29, the contact probe 100 placed immediately under asolder ball 72 moves upward and causes the conical end of the tipportion 121 to penetrate through the insulating layer formed on thesurface of the solder ball 72 so that electrical continuity with thesolder ball 72 can be secured.

However, as shown in FIG. 30, the contact probe 100 leaves a dent 53 onthe solder ball 72 after the measurement. As shown in FIG. 31, when thesolder ball 72 having the dent 53 is used for soldering with a padelectrode 73 on a circuit substrate 74, the dent 53 forms an enclosedspace surrounded by the solder ball 72 and the pad electrode 73. Whenthe assembly is heated for soldering under this condition, the air inthe enclosed dent 53 expands and may burst the solder ball 72. Thisphenomenon known as the “popcorn phenomenon” causes unsatisfactoryconnection, which is a serious problem.

A second prior art for a ball-shaped subject surface has proposed acontact probe 101 shown in FIG. 32. The contact probe 101 comprises apair of arms 114 that can open and close like a pair of tweezers. Eachof the arms 114 is provided at the tip portion with a claw 112 thatfaces the other claw 112. As shown by an arrow in FIG. 32, the contactprobe 101 rises from below. As shown in FIG. 33, the pair of arms 114move in a direction toward the closed position so that the claws 112 canengage with the solder ball 72 from the side. As a result, theinsulating layer on the surface of the solder ball 72 is broken, and theelectrical continuity between the contact probe 101 and the solder ball72 can be secured.

However, the contact probe 101 has a drawback. It is difficult to adjustthe closing movement of the arms 114 against the diameter of the solderball 72. If the degree of the closing of the arms 114 is insufficient,the claws 112 cannot penetrate sufficiently. Conversely, if the degreeof the closing of the arms 114 is excessive, the claws 112 penetrateexcessively, damaging the solder ball 72 or making themselves locked. Ifthe locking occurs, the claws 112 cannot be separated from the solderball 72. Consequently, when the contact probe 101 descends, the claws112 tear off the solder ball 72 from the BGA substrate 71, creating aproblem. The contact probe 101 has another drawback in that it requiresa complex mechanism for opening and closing the arms 114.

A third prior art for a ball-shaped subject surface has proposed acontact probe 102 shown in FIG. 34. The contact probe 102 has acylindrical tip portion whose upper end forms a sharp edge 115. When thecontact probe 102 is used, as shown by an arrow in FIG. 34, thecylindrical tip portion rises toward the solder ball 72. As a result, asshown in FIG. 35, the edge 115 penetrates through the insulating layeron the surface of the solder ball 72, securing the electrical continuitybetween the contact probe 102 and the solder ball 72.

However, it is difficult to produce with high precision the cylindricaltip portion of the contact probe 102. If the edge 115 has a diameterlarger than that of the solder ball 72 to a certain extent, the edge 115may push the solder ball 72 into the cylindrical tip portion of thecontact probe 102 without penetrating into the solder ball 72 as shownin FIG. 36. In this case, an accurate measurement cannot be conductedbecause the insulating layer on the surface of the solder ball 72 is notbroken. If this phenomenon occurs, when the contact probe 102 descends,it may tear off the solder ball 72 from the BGA substrate 71.

DISCLOSURE OF THE INVENTION

A general object of the present invention is to offer a method thatsecures reliable electrical contact with an electrode hidden underneathan insulating layer, such as a naturally formed oxide layer or resistresidues, existing on the surface of a subject surface. Accordingly, aparticular object of the present invention is to offer a contact probethat can secure electrical contact with the electrode by scrubbing awaythe insulating layer on the electrode such that the amount of shavingsadhering to the tip portion is reduced and the scratches formed on thesurface of the subject surface is decreased.

Another particular object is to offer a contact probe that can secureelectrical continuity by breaking the insulating layer formed on acurved subject surface of a ball-shaped electrode such as a solder ballwithout tearing off the ball-shaped electrode or excessively damagingit.

To attain the foregoing object, a contact probe (referred to as a firstcontact probe in this section of “Disclosure of the Invention”) inaccordance with an aspect of the present invention comprises:

-   -   (a) a tip portion that makes contact with a subject surface;    -   (b) a supporting portion that supports the other portions and        performs electrical connection; and    -   (c) a spring portion that connects the tip portion to the        supporting portion.        The tip portion of the first contact probe comprises:    -   (a) a contacting flat face that is provided at the tip of the        tip portion to make area contact with the subject surface;    -   (b) a first oblique face that is provided at one end of the        contacting flat face such that the angle between the first        oblique face and the contacting flat face is at least 90 degrees        and at most 170 degrees;    -   (c) a corner portion that is provided between the first oblique        face and the contacting flat face and that is rounded with a        first radius of curvature;    -   (d) a second oblique face that is provided at the other end of        the contacting flat face such that the angle between the second        oblique face and the contacting flat face is at least 90 degrees        and at most 170 degrees; and    -   (e) another corner portion that is provided between the second        oblique face and the contacting flat face and that is rounded        with a second radius of curvature larger than the first radius        of curvature.        In the first contact probe, the tip portion, the supporting        portion, and the spring portion are structured such that when        the supporting portion is fixed to an inspecting apparatus and        when the contacting flat face is pressed against the subject        surface, the elastic deformation of the spring portion produced        by the pressing force can move the tip portion with the first        oblique face in the lead maintaining the contact between the        contacting flat face and the subject surface. In this structure,        the side opposite to the side that moves in the lead during the        scrubbing by the pressing force has a corner portion with a        radius of curvature larger than that of the corner portion at        the opposite side. Consequently, this structure enables the        production of a contact probe that can sufficiently shave the        subject surface during the scrubbing by the pressing force so as        to secure the contact and that can reduce the amount of shavings        during the scrubbing while the contact probe dissociates from        the subject surface. Therefore, the contact probe can reduce the        amount of shavings adhering to the tip portion and decrease the        formation of scratches on the subject surface.

In the first contact probe, the second radius of curvature may be atleast two times the first radius of curvature. This structure enablesthe production of a contact probe that effectively reduces the amount ofshavings during the scrubbing while the contact probe dissociates fromthe subject surface. Therefore, the amount of shavings adhering to thetip portion can be reduced. As a result, the formation of scratches onthe subject surface can be reduced.

In the first contact probe, the first radius of curvature may be atleast 0.1 μm and at most 5 μm. This structure enables the production ofa contact probe that adequately shaves the subject surface during thescrubbing by the pressing force and effectively reduces the amount ofshavings during the scrubbing while the contact probe dissociates fromthe subject surface.

To attain the above-described object, another contact probe (referred toas a second contact probe in this section of “Disclosure of theInvention”) in accordance with another aspect of the present inventioncomprises:

-   -   (a) a tip portion that makes contact with a subject surface;    -   (b) a supporting portion that supports the other portions and        performs electrical connection; and    -   (c) a spring portion that connects the tip portion to the        supporting portion.        The tip portion of the second contact probe comprises:    -   (a) a first corner portion that is provided at one side of the        tip portion (hereinafter referred to as the first side) and that        is rounded with a first radius of curvature; and    -   (b) a second corner portion that is provided at the opposite        side of the tip portion (hereinafter referred to as the second        side), that is connected to the first corner portion at a        connecting point at the tip of the tip portion, and that is        rounded with a second radius of curvature different from the        first radius of curvature.        In the second contact probe, the tip portion, the supporting        portion, and the spring portion are structured such that when        the supporting portion is fixed to an inspecting apparatus and        when the tip portion is pressed against the subject surface, the        elastic deformation of the spring portion produced by the        pressing force can move the tip portion with the first side in        the lead maintaining the contact between the tip portion and the        subject surface. This structure enables the production of a        contact probe that removes the surface layer of the subject        surface during one of the two scrubbing actions (one is the        scrubbing by pressing the tip portion against the subject        surface and the other is the scrubbing during the dissociation        from the subject surface) so as to secure the electrical contact        and that reduces the amount of the removal of the surface layer        during the other scrubbing action.

In the second contact probe, the second radius of curvature may belarger than the first radius of curvature. This structure enables theproduction of a contact probe that sufficiently removes the surfacelayer of the subject surface during the scrubbing by the pressing forceand reduces the amount of removal during the scrubbing at the time ofthe dissociation.

In the second contact probe, the first side may be provided with asuppressing portion adjacent to the first corner portion. Thesuppressing portion presses against the subject surface a bulgingportion produced by the first corner portion. (If the bulging portiongrows and peels, it becomes a shaving.) This structure enables theprevention of the growth of the bulging portion produced by the firstcorner portion while the electrical contact is secured with the firstcorner portion. Consequently, the problem caused by the adherence of theshavings can be solved.

In the second contact probe, the suppressing portion at the first sidemay comprise at least one suppressing face that is opposed to thesubject surface. This structure enables the suppressing face to repelthe bulging portion toward the subject surface even when the directionof the growth of the bulging portion varies to some extent. In otherwords, this simple structure enables reliable suppression of the growthof the bulging portion.

In the second contact probe, the suppressing portion at the first sidemay comprise a plurality of the foregoing suppressing faces that areconnected in the form of a step-wise structure. This structure enablesone of the suppressing faces to function even when the initialinclination of the tip portion toward the first side is large to somedegree. In other words, this structure enables the production of acontact probe that suppresses the adverse effects caused by thevariation of the initial inclination of the tip portion.

The second contact probe may have the following features:

-   -   (a) the first radius of curvature is larger than the second        radius of curvature;    -   (b) the second side is provided with a suppressing portion        adjacent to the second corner portion; and    -   (c) the suppressing portion presses a bulging portion produced        by the second corner portion against the subject surface.        This structure enables the contact probe to secure the        electrical contact by the scrubbing at the time of the        dissociation of the tip portion from the subject surface, rather        than by the scrubbing at the time of pressing the tip portion        against the subject surface. The contact probe can suppress the        growth of the bulging portion during the scrubbing at the time        of the dissociation from the subject surface.

In the second contact probe, the suppressing portion at the second sidemay comprise a suppressing face that is opposed to the subject surface.In this structure, the bulging portion produced during the scrubbing atthe time of the dissociation from the subject surface can be repelledtoward the subject surface by the suppressing face. In other words, thissimple structure enables reliable suppression of the growth of thebulging portion.

To attain the above-described object, yet another contact probe(referred to as a third contact probe in this section of “Disclosure ofthe Invention”) in accordance with yet another aspect of the presentinvention comprises a tip portion for making contact with a ball-shapedelectrode of a subject to be measured. The tip portion is provided atits tip with a recess for allowing the ball-shaped electrode to comeinto the recess so that the tip portion can make contact with theball-shaped electrode. The recess is provided with:

-   -   (a) a bottom that limits the movement of the tip portion toward        the ball-shaped electrode by making contact with the ball-shaped        electrode;    -   (b) two oblique side walls; and    -   (c) at least one protrusion that protrudes from one of the        oblique side walls to scratch the ball-shaped electrode so that        the contact with the ball-shaped electrode can be attained.        This structure enables the production of a contact probe that        secures the electrical continuity needed for the measurement,        because the protrusion or each protrusion bites the side portion        of a ball-shaped electrode, such as one used in a BGA package,        to remove the insulating layer on the surface of the electrode        when the contact probe is pressed against the ball-shaped        electrode. In this case, the bottom of the recess makes contact        with the lowermost portion of the ball-shaped electrode so as to        prevent the protrusion or each protrusion from excessively        biting the electrode. As a result, the contact probe can avoid        the short-circuiting between the neighboring electrodes due to        an excessive burr. The contact probe can also avoid the locking        of the protrusion or each protrusion in the electrode due to an        excessive bite.

In the third contact probe, the protrusion or each protrusion may beprovided at a position shifted to the side by an angle of at least 45degrees and at most 90 degrees from the direction viewed from point Otoward point A, where point O is the center of the opening of therecess, and point A is the center of the bottom of the recess. Thisstructure enables the production of a contact probe that can scrub onlya proper distance on the ball-shaped electrode, thereby preventing thepopcorn phenomenon.

In the third contact probe, the protrusion or each protrusion may have aheight (from the root to the pointed end) of at most ¼ the radius of theball-shaped electrode. In this structure, the depth of the bite by theprotrusion or each protrusion into the ball-shaped electrode can belimited to a specified degree. As a result, this structure can avoid theshort-circuiting between the neighboring electrodes due to an excessiveburr.

In the third contact probe, the contact probe may further comprise:

-   -   (a) a supporting portion that supports the other portions and        performs electrical connection; and    -   (b) a spring portion that connects the tip portion to the        supporting portion.        In this case, the tip portion, the supporting portion, and the        spring portion may be formed as a unitary structure. This        structure enables the contact probe to be produced easily by the        LIGA process with high precision.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is an enlarged plan view showing a tip portion of a first exampleof the contact probe in Embodiment 1 according to the present invention.

FIG. 2 is an enlarged plan view showing a tip portion of a secondexample of the contact probe in Embodiment 1 according to the presentinvention.

FIG. 3 is a perspective view showing the second example of the contactprobe in Embodiment 1 according to the present invention.

FIG. 4 is an enlarged plan view showing a tip portion of the contactprobe in Embodiment 2 according to the present invention.

FIG. 5 is an enlarged plan view showing a tip portion of the contactprobe in Embodiment 3 according to the present invention.

FIG. 6 is a first diagram illustrating a phenomenon occurring in thevicinity of a corner portion having no suppressing portion.

FIG. 7 is a second diagram illustrating the phenomenon occurring in thevicinity of a corner portion having no suppressing portion.

FIG. 8 is a first diagram illustrating a phenomenon occurring in thevicinity of a corner portion having a suppressing portion.

FIG. 9 is a second diagram illustrating the phenomenon occurring in thevicinity of a corner portion having a suppressing portion.

FIG. 10 is an enlarged plan view showing a tip portion of the contactprobe in Embodiment 4 according to the present invention.

FIG. 11 is an enlarged plan view showing a tip portion of the contactprobe in Embodiment 5 according to the present invention.

FIG. 12 is a diagram illustrating a first example of the contact probeaccording to the prior art.

FIG. 13 is a diagram illustrating a second example of the contact probeaccording to the prior art.

FIG. 14 is an enlarged plan view showing a tip portion of the contactprobe according to the prior art.

FIG. 15 is a first diagram illustrating the function of the contactprobe according to the prior art.

FIG. 16 is a second diagram illustrating the function of the contactprobe according to the prior art.

FIG. 17 is a third diagram illustrating the function of the contactprobe according to the prior art.

FIG. 18 is a further enlarged plan view showing a tip portion of thecontact probe according to the prior art.

FIG. 19 is a perspective view showing a first contact probe inEmbodiment 6 according to the present invention.

FIG. 20 is an enlarged plan view showing a tip portion of the firstcontact probe in Embodiment 6 according to the present invention.

FIG. 21 is a cross-sectional view showing a situation in which ameasurement is conducted through a solder ball by using the firstcontact probe in Embodiment 6 according to the present invention.

FIG. 22 is a first diagram illustrating an operating condition of acontact probe conceived as a comparative example in Embodiment 6.

FIG. 23 is a second diagram illustrating another operating condition ofthe contact probe conceived as a comparative example in Embodiment 6.

FIG. 24 is a diagram illustrating a situation in which the neighboringburrs make contact with each other when the measurement is conducted byusing the contact probe conceived as a comparative example in Embodiment6.

FIG. 25 is an enlarged plan view showing a tip portion of a secondcontact probe in Embodiment 6 according to the present invention.

FIG. 26 is a cross-sectional view showing a situation in which ameasurement is conducted through a solder ball by using the secondcontact probe in Embodiment 6 according to the present invention.

FIG. 27 is a diagram illustrating the position of the claws of the firstcontact probe in Embodiment 6 according to the present invention.

FIG. 28 is a front view showing an ordinary BGA package.

FIG. 29 is a diagram illustrating an example of the usage of a firstcontact probe of the prior art for a ball-shaped subject surface.

FIG. 30 is a cross-sectional view showing a solder ball after ameasurement is conducted by using the first contact probe of the priorart for a ball-shaped subject surface.

FIG. 31 is a cross-sectional view showing a situation in which a solderball is used for soldering after a measurement is conducted by using thefirst contact probe of the prior art for a ball-shaped subject surface.

FIG. 32 is a first diagram illustrating an example of the usage of asecond contact probe of the prior art for a ball-shaped subject surface.

FIG. 33 is a second diagram illustrating the example of the usage of thesecond contact probe of the prior art for a ball-shaped subject surface.

FIG. 34 is a first diagram illustrating an example of the usage of athird contact probe of the prior art for a ball-shaped subject surface.

FIG. 35 is a second diagram illustrating the example of the usage of thethird contact probe of the prior art for a ball-shaped subject surface.

FIG. 36 is a cross-sectional view showing a situation in which a solderball is pushed into the cylindrical tip portion when a measurement isconducted by using the third contact probe of the prior art for aball-shaped subject surface.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 18 is an enlarged view of the tip portion 1 of a conventionalcontact probe. The boundary between the contacting flat face 10 and theoblique face 15 at each end of the contacting flat face 10 forms acorner portion 16. In the conventional contact probe, the shape and sizeof the corner portion 16 are determined without paying much attention.The corner portions 16 are symmetrically formed without regard to themoving direction for the scrubbing when the tip portion 1 is pressedagainst the subject surface. On the other hand, the present inventorscarefully considered the size of the corner portion and accomplished thepresent invention.

EMBODIMENT 1

(Structure)

A contact probe in Embodiment 1 according to the present invention isexplained below by referring to FIG. 1. FIG. 1 is an enlarged view ofthe tip portion 1. In the contact probe, a first oblique face 11 refersto an oblique face that moves in the lead when the tip portion 1 movesfor performing the scrubbing by the force pressing the contact probeagainst the subject surface. As shown in FIG. 1, the first oblique face11 is located at the left hand side of the contacting flat face 10. Theopposite oblique face is referred to as a second oblique face 12. Acorner portion 13 through which one end of the contacting flat face 10is connected to the first oblique face 11 has a radius of curvaturedifferent from that of a corner portion 14 through which the other endof the contacting flat face 10 is connected to the second oblique face12. As can be seen from FIG. 1, the corner portion 14 has the radius ofcurvature R2 larger than the radius of curvature R1 of the cornerportion 13.

(Function and Effect)

As explained above, the side opposite to the side that performs thescrubbing by the pressing force has a corner portion with a radius ofcurvature larger than that of the corner portion at the other side.Consequently, when the contact probe is used, the subject surface can besufficiently shaved during the scrubbing by the pressing force so as tosecure the electrical continuity, and the amount of shavings can bereduced during the scrubbing while the contact probe dissociates fromthe subject surface. Therefore, the amount of shavings adhering to thetip portion can be reduced. As a result, this structure can increase thenumber of times the contact probe can be used continuously withoutcleaning.

As mentioned above, the formation of scratches can be suppressed duringthe scrubbing while the contact probe dissociates from the subjectsurface. Therefore, this structure can reduce the extent of thescratches formed on the surface of the electrode in each measurement,thereby reducing the number of occurrences of unsatisfactory connectionin the subsequent bonding step.

Although the difference in radius of curvature shown in FIG. 1 exercisessome effects, the difference can be increased. FIG. 2 shows an examplein which the difference is increased. FIG. 3 shows an overview of thecontact probe having the foregoing tip portion 1. An increaseddifference as shown in FIG. 2 increases the effect of reduction in theamount of adhering shavings and the formation of scratches during thescrubbing at the time of the dissociation. The present inventors foundthat the effect is increased when the radius of curvature of the cornerportion 14 is at least two times that of the corner portion 13.Furthermore, when R1 is at least 0.1 μm and at most 5 μm, the effect isobvious. In particular, when R1 is at least 0.5 μm and at most 3 μm, theeffect is more obvious. When an angle produced by each of the cornerportions 13 and 14 is at least 90 degrees and at most 170 degrees, theeffect is sufficient. If the angle is larger than 170 degrees, theshavings tend to accumulate between the tip portion and the subjectsurface, thereby decreasing the reliability.

The angles produced by the corner portions 13 and 14 may be either thesame or different. The contact probe can be produced by the LIGA processas a unitary structure. Consequently, the radius of curvature and theangle at the corner portions of the tip portion can be freely adjustedby changing the mask pattern.

EMBODIMENT 2

(Structure)

A contact probe in Embodiment 2 according to the present invention isexplained below by referring to FIG. 4. FIG. 4 is an enlarged view ofthe tip portion 1. During the scrubbing by pressing the contact probeagainst the subject surface, the tip portion 1 moves to the left in FIG.4. Hereinafter, the side that moves in the lead in this direction isreferred to as “the first side,” and the opposite side (right hand sidein FIG. 4) is referred to as “the second side.” Therefore, the secondside represents the side that moves in the lead during the scrubbing atthe time of the dissociation of the contact probe from the subjectsurface.

As shown in FIG. 4, the tip portion 1 of the contact probe has nocontacting flat face 10 described in Embodiment 1 (see FIGS. 1 and 2).The tip portion 1 has a corner portion 13 (from point B to point D) as afirst corner portion at the first side and a corner portion 14 (frompoint B to point C) as a second corner portion at the second side. Thetwo corner portions are connected at point B.

The corner portions 13 and 14 have a different radius of curvature. Thecorner portion 13 has the radius of curvature r, and the corner portion14 has the radius of curvature R. As can be seen from FIG. 4, R isgreater than r. The magnitude of R is determined so as not to produceshavings at the intended contacting force, and the magnitude of r isdetermined so as to secure electrical contact by shaving the subjectsurface at the intended contacting force. The center of the curvature ofthe corner portion 14 is expressed as point O. A first oblique face 11is connected to the corner portion 13 at point D, and a second obliqueface 12 is connected to the corner portion 14 at point C.

In this contact probe, the nearest point to the subject surface beforemaking contact with the subject surface is referred to as the initiallowermost point A. The initial lowermost point A lies at some midpointin the corner portion 13, i.e., somewhere between the connecting point Band point D. When the supporting portion 3 is fixed to an inspectingapparatus and when the contact probe descends vertically toward thesubject surface, the initial lowermost point A first makes contact withthe subject surface. Then, the elastic deformation of the spring portion2 slants the entire tip portion 1 in a clockwise direction in FIG. 4. Asa result, the center of the contact of the tip portion 1 with thesubject surface shifts to a pressurized lowermost point that is slightlyaway from the initial lowermost point A to the right. Under thiscondition, the tip portion 1 moves with the first side in the lead (tothe left in FIG. 4) maintaining the contact with the subject surface,performing the scrubbing.

It is desirable that the pressurized lowermost point be coincident withthe connecting point B. More specifically, it is desirable that themagnitude, Φ, of the angle AOB be equal to the angle of inclination ofthe tip portion 1 when the intended contacting force against the subjectsurface is attained. The reason is that when the pressurized lowermostpoint is coincident with the connecting point B, the entire cornerportion 13 shaves the subject surface during the scrubbing by pressingthe contact probe against the subject surface, thereby contributing tothe securing of the required electrical contact.

However, the angle of inclination of the tip portion 1 may vary inreality. Taking the variation into account, it is desirable that thepressurized lower-most point lie in the range from the connecting pointB to point C inclusive. More specifically, the magnitude, Θ, of theangle AOC must be larger than the maximum angle of inclination of thetip portion 1 when the supporting portion 3 is brought to the nearestposition to the subject surface, i.e., when the spring portion 2 iselastically deformed to the maximum. The reason is that if the tipportion 1 is inclined at an angle larger than Θ by the force pressing itagainst the subject surface, the oblique face 12 makes contact with thesubject surface. As a result, the electrical contact cannot be securedbecause the subject surface cannot be shaved properly.

(Function and Effect)

As explained above, Embodiment 2 can attain an effect similar to thatattained in Embodiment 1, because the side opposite to the side thatperforms the scrubbing by the pressing force has a corner portion with aradius of curvature larger than that of the corner portion at theopposite side.

EMBODIMENT 3

(Structure)

A contact probe in Embodiment 3 according to the present invention isexplained below by referring to FIG. 5. FIG. 5 is an enlarged view ofthe tip portion 1. As with the contact probe explained in Embodiment 2,this contact probe has the lowermost point A, a connecting point B, acorner portion 13 as a first corner portion, a corner portion 14 as asecond corner portion, a first oblique face 11, a second oblique face12, and point O as the center of the curvature of the corner portion 14.However, unlike the contact probe in Embodiment 2, the contact probe inEmbodiment 3 has a suppressing portion between the corner portion 13 andthe first oblique face 11. The suppressing portion is provided tosuppress to the subject surface a bulging portion produced from thesubject surface by the corner portion 13. The suppressing portionextends from the corner portion 13 toward the first side and includes asuppressing face 41 (from point E to point F) that is opposed to thesubject surface. The height h of the suppressing face from the lowermostpoint A must not exceed the limit that can prevent the bulging portionfrom extending to the outside of the suppressing portion. If the heighth is excessively large, the bulging portion extends to the outsidewithout being pressed properly against the subject surface. If theheight h is excessively small, a problem may be created by the variationof the initial inclination of the tip portion 1 in a counterclockwisedirection. More specifically, if the variation is large to a certainextent, the large initial inclination may cause the corner portion 13 dbetween the suppressing face 41 and the first oblique face 11 to makecontact with the subject surface and undesirably produce shavings. Theheight h must be sufficiently large in so that the variation of theinitial inclination of the tip portion 1 disallows the corner portion 13d to make contact with the subject surface and must be sufficientlysmall to prevent the bulging portion produced by the corner portion 13from extending to the outside.

(Function and Effect)

The function of the suppressing portion is explained below by referringto FIGS. 6 to 9. FIGS. 6 and 7 are enlarged views showing the portion inthe vicinity of the corner portion 13 when no suppressing portion isprovided. First, the tip portion 1 proceeds with the first side in thelead (to the left-hand side in the views) maintaining the contact withthe subject surface 20. As shown in FIG. 6, the corner portion 13scrapes the material in the surface layer of the subject surface 20,forming a bulging portion 23. The bulging portion 23 is squeezed in adirection shown by an arrow 44. As shown in FIG. 7, the bulging portion23 continues to grow along the first oblique face 11. When the bulgingportion 23 grows to a certain limit, the stress concentrated at thebulging portion 23's root portion facing the corner portion 13 reaches acritical point, forming a broken section 46. After the breaking, thebulging portion 23 becomes a shaving and adheres to an undesirableportion of the tip portion 1 like the shavings 23 shown in FIGS. 16 and17, creating a problem.

On the other hand, FIGS. 8 and 9 are enlarged views showing the portionin the vicinity of the corner portion 13 when a suppressing portion isprovided. First, the tip portion 1 proceeds with the first side in thelead (to the left-hand side in the views) maintaining the contact withthe subject surface 20. As shown in FIG. 8, the corner portion 13scrapes the material in the surface layer of the subject surface 20,forming a bulging portion 23. The bulging portion 23 is first squeezedin a direction shown by an arrow 44. Unlike the case shown in FIGS. 6and 7, a suppressing face 41 of the suppressing portion is provided soas to be opposed to the subject surface 20 at a position ahead of thegrowing bulging portion 23. Consequently, the leading end of the bulgingportion 23 is blocked by the suppressing face 41 and repelled toward thesubject surface 20 as shown by an arrow 47 in FIG. 9. Because the heighth of the suppressing face 41 (see FIG. 5) is sufficiently small in orderfor the bulging portion 23 not to extend to the outside, the bulgingportion 23 is pressed against the subject surface 20 without growingfurther. Because the region S in which the bulging portion 23 makescontact with the tip portion 1 is broadened, the stress is dispersed.Thus, the suppression of the growth of the bulging portion 23 canprevent the bulging portion 23 from adhering to the tip portion 1 as ashaving, thereby avoiding the creation of a problem.

As can be seen from FIG. 5, not only can the contact probe in Embodiment3 attain the same effect as attained in Embodiment 2 but it can alsosuppress the growth of a bulging portion because it is provided with thesuppressing portion including the suppressing face 41 between the cornerportion 13 and the first oblique face 11. As a result, it can solve thehitherto unsolved problem caused by shavings.

EMBODIMENT 4

(Structure)

A contact probe in Embodiment 4 according to the present invention isexplained below by referring to FIG. 10. FIG. 10 is an enlarged view ofthe tip portion 1. As with the contact probe explained in Embodiment 3,this contact probe has the lowermost point A, a connecting point B, acorner portion 13 as a first corner portion, a corner portion 14 as asecond corner portion, a first oblique face 11, a second oblique face12, and point O as the center of the curvature of the corner portion 14.Furthermore, it has a suppressing portion between the corner portion 13and the first oblique face 11. However, unlike the contact probe inEmbodiment 3, whose suppressing portion includes only one suppressingface, 41, the contact probe in Embodiment 4 has a suppressing portionincluding a plurality of suppressing faces, 41 a, 41 b, and 41 c, whichare connected in the form of a step-wise structure. A corner portion 13a is provided between the suppressing faces 41 a and 41 b, and a cornerportion 13 b between the suppressing faces 41 b and 41 c. A cornerportion 13 c is provided between the suppressing face 41 c and the firstoblique face 11. The suppressing faces 41 a, 41 b, and 41 c have alength of L1, L2, and L3, respectively. Their relationship is expressedas L1>L2>L3.

Although the suppressing portion includes three suppressing faces inthis case, the number of suppressing faces may be changed.

(Function and Effect)

A structure having a plurality of suppressing faces as described abovecan produce a contact probe that not only has the effects attained inEmbodiment 3 but also suppresses the adverse effects caused by thevariation of the initial inclination of the tip portion. This process isexplained below by referring to FIG. 10.

In an ideal state, the initial inclination of the tip portion 1 is zero,and the subject surface 20 first makes contact with the tip portion 1 atthe lowermost point A in a posture indicated by the line AX. After thepressing force inclines the tip portion 1 slightly in a clockwisedirection, the corner portion 13 scrapes the subject surface 20. Whilethe suppressing face 41 a suppresses the growth of the bulging portion,the tip portion 1 moves with the first side in the lead (to theleft-hand side in FIG. 10).

In FIG. 10, the line HG is a tangent common to the corner portions 13and 13 a, and α denotes an angle produced by the lines HG and AX. Theline IJ is a tangent common to the corner portions 13 a and 13 b, and βdenotes an angle produced by the lines IJ and AX. The line MN is atangent common to the corner portions 13 b and 13 c, and γ denotes anangle produced by the lines MN and AX.

If the initial inclination of the tip portion 1 in a counterclockwisedirection is smaller than α, the subject surface 20 makes no contactwith the corner portion 13 a. Consequently, the corner portion 13scrapes the subject surface 20, and the suppressing face 41 a cansuppress the growth of the bulging portion.

If the initial inclination of the tip portion 1 in a counterclockwisedirection is α or more and less than β, the subject surface 20 makescontact with the corner portion 13 a without making contact with thecorner portion 13 b. Consequently, the corner portion 13 a scrapes thesubject surface 20, and the suppressing face 41 b can suppress thegrowth of the bulging portion.

If the initial inclination of the tip portion 1 in a counterclockwisedirection is β or more and less than γ, the subject surface 20 makescontact with the corner portion 13 b without making contact with thecorner portion 13 c. Consequently, the corner portion 13 b scrapes thesubject surface 20, and the suppressing face 41 c can suppress thegrowth of the bulging portion.

If the initial inclination of the tip portion 1 in a counterclockwisedirection is γ or more, the subject surface 20 makes contact with thecorner portion 13 c. Consequently, the corner portion 13 c scrapes thesubject surface 20, and the growth of the bulging portion cannot besuppressed.

As explained above, when the suppressing portion has only onesuppressing face, 41 a, the growth of the bulging portion can besuppressed only when the angle of the initial inclination of the tipportion 1 in a counterclockwise direction is less than α. On the otherhand, when the suppressing portion has three suppressing faces, theangle that enables the suppression of the growth of the bulging portioncan be extended to γ. In other words, an increase in the number ofsuppressing faces by forming a step-wise structure enables theproduction of a contact probe that more effectively suppresses theadverse effects caused by the variation of the initial inclination of atip portion in a counter-clockwise direction.

EMBODIMENT 5

(Structure)

A contact probe in Embodiment 5 according to the present invention isexplained below by referring to FIG. 11. FIG. 11 is an enlarged view ofthe tip portion 1. This contact probe also moves to the left in FIG. 11with “the first side” in the lead during the scrubbing by pressing thecontact probe against the subject surface. It moves to the right in FIG.11 with “the second side” in the lead during the scrubbing at the timeof the dissociation of the contact probe from the subject surface. Thiscontact probe is devised to secure the electrical contact during thescrubbing at the time of the dissociation from the subject surfacerather than during the scrubbing at the time of pressing the contactprobe against the subject surface.

This contact probe has the tip portion 1 provided with a corner portion17 (from point B to point C) as a first corner portion existing in thefirst side and a corner portion 18 (from point B to point D) as a secondcorner portion existing in the second side. The corner portions 17 and18 are connected with each other at the connecting point B.

The corner portions 17 and 18 have a different radius of curvature. Thecorner portion 17 has the radius of curvature R, and the corner portion18 has the radius of curvature r. As can be seen from FIG. 11, R isgreater than r. The center of the curvature of the corner portion 17 isexpressed as point O. A first oblique face 11 is connected to the cornerportion 17 at point C, and a second oblique face 12 is connected to acorner portion 19. A suppressing face 41 is provided between the cornerportion 19 and point D at the end of the corner portion 18.

In this contact probe, the nearest point to the subject surface beforemaking contact with the subject surface is referred to as the initiallowermost point A. The initial lowermost point A lies at some midpointin the corner portion 17, i.e., somewhere between the connecting point Band point C. When the supporting portion 3 is fixed to an inspectingapparatus and when the contact probe descends vertically toward thesubject surface, the initial lowermost point A first makes contact withthe subject surface. Then, the elastic deformation of the spring portion2 slants the entire tip portion 1 in a clockwise direction in FIG. 11.As a result, the center of the contact of the tip portion 1 with thesubject surface shifts to the pressurized lowermost point that isslightly away from the initial lowermost point A to the right. Underthis condition, the tip portion 1 moves with the first side in the lead(to the left in FIG. 11) maintaining the contact with the subjectsurface, performing the scrubbing. However, the corner portion 17 havingthe radius of curvature R produces no shavings.

On the other hand, when the contact probe dissociates from the subjectsurface 20, the tip portion 1 moves with the second side in the lead (tothe right in FIG. 11) scraping the subject surface 20 with the cornerportion 18. As described above, the suppressing face 41 is provided inthe second side at the right of the corner portion 18. A bulging portionproduced by the corner portion 18 is pressed against the subject surface20 by the suppressing face 41, and its growth is suppressed. The heighth of the suppressing face 41 from the connecting point B must not exceedthe limit that can prevent the bulging portion from extending to theoutside of the suppressing portion. If the height h is excessivelylarge, the bulging portion extends to the outside without being pressedproperly against the subject surface.

An angle, Ψ, is produced by two lines; one is a tangent common to thecorner portions 18 and 19 and the other is the subject surface 20 whenit first makes contact with the corner portion 17 at the lowermost pointA. The angle Ψ must be larger than the maximum angle of inclination ofthe tip portion 1 when the supporting portion 3 is brought to thenearest position to the subject surface, i.e., when the spring portion 2is elastically deformed to the maximum. The reason is that if the tipportion 1 is inclined at an angle larger than Ψ by the force pressing itagainst the subject surface 20, the corner portion 19 makes contact withthe subject surface 20, scraping the subject surface 20.

It is desirable that the pressurized lowermost point be coincident withthe connecting point B. More specifically, it is desirable that themagnitude, Φ, of the angle AOB be equal to the angle of inclination ofthe tip portion 1 when the intended contacting force against the subjectsurface is attained. The reason is that when the pressurized lowermostpoint is coincident with the connecting point B, the scrubbing at thetime of the dissociation of the contact probe from the subject surfacecan be started in the state that allows the entire corner portion 18 toscrape the subject surface. This condition is advantageous in securingthe required electrical contact.

(Function and Effect)

As explained above, the structure in Embodiment 5 enables the productionof a contact probe that not only secures the electrical contact duringthe scrubbing at the time of the dissociation from the subject surfacerather than during the scrubbing at the time of pressing the contactprobe against the subject surface but also suppresses the growth of thebulging portion during the scrubbing at the time of the dissociation.

Embodiments 2 to 5 are explained above for a structure in which thefirst corner and the second corner are connected by the connecting pointB rather than by the contacting flat face 10 explained in Embodiment 1(see FIG. 1). Notwithstanding the foregoing explanations, the contactingflat face 10 may be employed in place of the connecting point B withoutchanging the concept of Embodiments 2 to 5.

EMBODIMENT 6

(Structure)

A contact probe in Embodiment 6 according to the present invention isexplained below by referring to FIGS. 19 and 20. As shown in FIG. 19, acontact probe 80 comprises a tip portion 51, a spring portion 52, and asupporting portion 53. The tip portion 51 is provided to make contactwith a subject having a ball-shaped electrode such as a solder ball. Theshape of the tip portion 51 is explained in detail below. The tipportion 51 is connected to the supporting portion 53 through the springportion 52. The contact probe 80 is formed as a unitary structure by thelithographie galvanoformung abformung (LIGA) process. The LIGA processfor producing a contact probe is explained, for example, in thepublished Japanese patent application Tokukai 2001-343397. According tothe process, a contact probe is produced by the following process. Aresist layer is formed on the surface of a substrate. The resist layeris processed so as to have an intended pattern by lithography. A metallayer is formed by plating at the area where the resist layer isremoved. Finally, the metal-layer portion is separated from the otherportions to obtain the contact probe. When produced by this process, thecontact probe has a shape in which a specified planar pattern has nearlyuniform thickness, as shown in FIG. 19. Consequently, the contact probethus produced has the tip portion 51 and the supporting portion 53 bothbasically in the shape of a rectangular solid rather than a cylindricalcolumn conventionally produced by machining.

FIG. 20 is an enlarged plan view showing the tip portion 51 of thecontact probe 80 shown in FIG. 19. The tip portion 51 has a recess 60 atits tip. The recess 60 has the shape of an inverted isosceles trapezoidwith a flat bottom 61 at the innermost portion. The bottom 61 isprovided to make contact with the ball-shaped electrode of the subjectto be measured so that the movement of the tip portion 51 toward theelectrode can be limited. In other words, the bottom 61 acts as astopper. A claw 62 protrudes from each oblique side wall of the recess60. The claws 62 can be formed as part of the unitary structure when thecontact probe 80 is formed by the LIGA process.

(Function and Effect)

The function of the contact probe 80 is explained below by referring toFIG. 21. FIG. 21 shows a situation in which the contact probe 80 makeselectrical contact with a solder ball 72 as a ball-shaped electrodeplaced on the undersurface of a BGA substrate 71. When the tip portion51 is pressed in a direction shown by an arrow, the recess 60 allows theentry of the solder ball 72, causing the claws 62 to bite the solderball 72. In this case, the movement of the solder ball 72 is limited bythe bottom 61 so that the depth of the bite by the claws 62 can belimited to a specified magnitude.

Here, as a comparative example against the contact probe 80, a contactprobe is conceived without providing the foregoing bottom 61 acting as astopper. For example, FIG. 22 shows a contact probe 103 provided withfixed bar- or board-shaped members having claws 112 facing each other atthe upper ends of the members. As the contact probe 103 advances towardthe solder ball 72 as shown by an arrow in FIG. 22, the claws 112 bitethe solder ball 72. In this case, the absence of the bottom 61 acting asa stopper produces the condition under which the depth of the bite bythe claws 112 is determined solely by the advancing distance of thecontact probe 103. As a result, the claws 112 tend to bite the solderball 72 excessively. Furthermore, as shown in FIG. 23, the claws 112deform the solder ball 72 by pressing the side portions of the solderball 72 with the upper sides of the claws 112 rather than sticking intothe solder ball 72. Consequently, burrs 75 are likely to be formed. Evenafter the contact probe 103 dissociates from the solder ball 72, theburrs 75 remain there without changing their shape. If the remainingburrs 75 are large to a certain extent, the neighboring burrs 75 of thesolder balls 72 arranged with a small pitch may make contact with eachother as shown in FIG. 24, creating a short-circuit problem.

On the other hand, the contact probe 80 explained by referring to FIGS.19 to 21 is provided with the tip portion 60 having the bottom 61 actingas a stopper. The bottom 61 can prevent the claws 62 from biting thesolder ball 72 excessively. Therefore, even if burrs are produced, theirsize is limited, and the short-circuiting can be avoided.

As explained above, the claws 62 are provided on the side walls of therecess 60 rather than on the bottom 61. As the tip portion 51 advances,the claws 62 scratch the solder ball 72 removing the insulating layer onthe surface and engage with the solder ball 72. In other words, theclaws 62 can perform scrubbing to secure the electrical continuity.Consequently, the dents are formed not at the lowermost portion of thesolder ball 72 but at a place slightly shifted to the side. Therefore,this structure can avoid the “popcorn phenomenon” caused by the dents.

As for the shape of the recess on the tip portion, the recess 60 shownin FIGS. 19 to 21 has a nearly trapezoidal shape with a flat bottom andflat oblique faces. However, the shape is not limited to this type. Forexample, an arc-shaped recess 60 h as shown in FIG. 25 may be employed.In this case, the innermost portion (referred to as 61 h) of the recess60 h acts as a stopper as shown in FIG. 26.

In the above explanation, the recess has two bilaterally symmetricalclaws 62 without regard to its shape. Nevertheless, it may haveasymmetrically arranged claws. Moreover, the number of claws has nolimitations providing that at least one claw is provided.

Next, the position of the claws 62 in the recess 60 is explained byreferring to FIG. 27. The position of the claw 62 as a protrusion can beexpressed as position B that is shifted to the side by an angle of θfrom the direction viewed from point O toward point A, where point O isthe center of the opening of the recess 60, and point A is the center ofthe bottom 61. In this case, the rotational coordinate is establishedfor each claw such that a positive value of θ0 is given to each claw.The present inventors found that when the angle θ is at least 45 degreesand at most 90 degrees, a satisfactory result can be attained. If theangle θ is less than 45 degrees, the claw 62 sticks into the solder ball72 in the vicinity of the lowermost position of the solder ball 72,creating the possibility of the popcorn phenomenon. If the angle θ ismore than 90 degrees, the claw 62 scrubs the solder ball 72 for aneedlessly long distance. On the other hand, when the angle θ is atleast 45 degrees and at most 90 degrees, the solder ball 72 can bescrubbed for a proper distance, and the popcorn phenomenon can beprevented.

In addition, the present inventors found that when the height H (fromthe root to the pointed end) of the claw 62 as a protrusion is at most ¼the radius of the solder ball 72 as a subject ball-shaped electrode, thedevelopment of the burrs can be most effectively prevented. If theheight H is more than ¼ the radius of the solder ball 72, the depth ofbite by the claw into the solder ball increases needlessly, creating aproblem of burring. On the other hand, when the height H is less than ¼the radius of the solder ball 72, the creation of the burring problemcan be suppressed.

The position and height of the claw are explained above by referring tothe trapezoidal recess 60 as shown in FIG. 27. The same explanation isto be applied not only to the arc-shaped recess 60 h as shown in FIG. 25but also to a recess having a different shape.

Unlike conventional contact probes produced by machining, the contactprobe produced as a unitary structure by the LIGA process isadvantageous in that it can be easily produced with high precision interms of the position, direction, height, etc. of the claw withoutregard to the number of claws.

The embodiments disclosed in this specification are to be considered inall respects as illustrative and not restrictive. The scope of thepresent invention is indicated by the following claims rather than bythe foregoing description. All changes that come within the meaning andrange of equivalency of the claims are therefore intended to be embracedin the scope of the present invention.

INDUSTRIAL APPLICABILITY

A contact probe of the present invention is provided with a tip portionhaving two corner portions. The one opposite to the other one that movesin the lead during the scrubbing by the pressing force has a radius ofcurvature larger than that of the other one. Consequently, whereas thescrubbing by the pressing force sufficiently removes the surface layerof the subject surface to secure the electrical contact, the scrubbingat the time of dissociation can reduce the amount of removal. As aresult, the contact probe can minimize the production of shavings andreduce the scratches on the subject surface.

Another contact probe of the present invention for a ball-shapedelectrode is provided with a tip portion having a recess. The recess isprovided with a specific protrusion and a bottom. The protrusion bitesthe side portion of a ball-shaped electrode, such as one used in a BGApackage, to remove the insulating layer on the surface of the electrode.Thus, electrical continuity needed for the measurement can be secured.The bottom of the recess makes contact with the lowermost portion of theball-shaped electrode to limit the movement of the tip portion, therebypreventing the protrusion from excessively biting the electrode. As aresult, the contact probe can avoid the short-circuiting between theneighboring electrodes due to an excessive burr. The contact probe canalso avoid the locking of the protrusion in the electrode due to anexcessive bite.

The invention claimed is:
 1. A contact probe, comprising: (a) a tipportion that makes contact with a subject surface, the tip portioncomprising: (a1) a first corner portion that is provided at one side ofthe tip portion (hereinafter referred to as the first side) and that isrounded with a first radius of curvature; and (a2) a second cornerportion that is provided at the opposite side of the tip portion(hereinafter referred to as the second side), that is connected to thefirst corner portion at a connecting point at the tip of the tipportion, and that is rounded with a second radius of curvature differentfrom the first radius of curvature; (b) a supporting portion thatsupports the other portions and performs electrical connection; and (c)a spring portion that connects the tip portion to the supportingportion; the tip portion, the supporting portion, and the spring portionbeing structured such that when the supporting portion is fixed to aninspecting apparatus and when the tip portion is pressed against thesubject surface, the elastic deformation of the spring portion producedby the pressing force can move the tip portion with the first side inthe lead maintaining the contact between the tip portion and the subjectsurface, wherein the first side is provided with a suppressing portionadjacent to the first corner portion, and the suppressing portionpresses against the subject surface a bulging portion produced by thefirst corner portion and the second radius of curvature is larger thanthe first radius of curvature.
 2. A contact probe as defined by claim 1,wherein the suppressing portion comprises at least one suppressing facethat is opposed to the subject surface.
 3. A contact probe as defined byclaim 2, wherein the suppressing portion comprises a plurality of thesuppressing faces that are connected in the form of a step-wisestructure.
 4. A contact probe as defined by claim 1, wherein: (a) thefirst radius of curvature is larger than the second radius of curvature;(b) the second side is provided with a suppressing portion adjacent tothe second corner portion; and (c) the suppressing portion presses abulging portion produced by the second corner portion against thesubject surface.
 5. A contact probe as defined by claim 4, wherein thesuppressing portion comprises a suppressing face that is opposed to thesubject surface.